Humans have a sense of self, and a sense of other – other people. It’s part of how our brains work.
The senses of self and other as teleological beings—meaning understood as purposeful or goal-directed agents—are not localized to a single brain area, but instead emerge from the interaction of multiple brain regions across several networks. However, neuroscience has identified key core regions involved in these processes:
Sense of Self (especially as a teleological agent):
Medial Prefrontal Cortex (mPFC): Critical for self-referential thought, introspection, autobiographical memory, and personal goals. Also involved in evaluating one’s own intentions and internal states. Strongly active during rest (“default mode”) and self-reflection.
Posterior Cingulate Cortex (PCC) & Precuneus: Part of the Default Mode Network (DMN), crucial for reflective thought, imagining oneself, and narrative self-continuity. Involved in integrating self-related experiences over time.
Temporoparietal Junction (TPJ): Left TPJ: Sometimes involved in distinguishing one’s own agency. Right TPJ: Especially important for self-other distinction, crucial for attributing mental states and perspectives to the self.
Insula: Processes interoception (internal bodily awareness), contributing to the sense of self as embodied. Linked to subjective emotional experience and awareness of agency.
Sense of Other (as a teleological agent):
Right Temporoparietal Junction (rTPJ): Key node in Theory of Mind (ToM); involved in understanding others’ beliefs, intentions, and goals. Crucial for distinguishing self from other and attributing independent agency.
Medial Prefrontal Cortex (again): Plays a dual role: helps model both one’s own and others’ mental states. Especially active during mentalizing (inferring intentions).
Superior Temporal Sulcus (STS): Detects biological motion and intentional actions of others. Helps infer purpose behind others’ movements and behavior.
Anterior Cingulate Cortex (ACC): Supports empathy, error monitoring, and social evaluation of others’ behaviors.
Network-level Summary:
- Default Mode Network (DMN):
Key for self-referential thinking and simulating other minds. - Social Cognition Network / Theory of Mind Network:
Includes the mPFC, TPJ, STS, and temporal poles; essential for understanding others as intentional agents. - Mirror Neuron System (premotor cortex, inferior parietal lobule):
Supports embodied simulation—understanding others’ actions via mirroring.
Integration:
The teleological sense of self and other likely arises from the interaction between the DMN and social cognition networks, coordinated by prefrontal and parietal hubs. These systems allow us to:
- Represent our own intentions as part of a coherent narrative.
- Model others’ goals as purpose-driven.
- Distinguish agency between self and other.
The Consequences of Damage
Damage to the brain regions involved in self/other representation disrupts core aspects of agency, mentalizing, and identity, often with striking consequences. Below is a region-by-region breakdown of how damage impairs the sense of self, other, and their distinction—with examples of symptoms and behaviors from both clinical and experimental observations.
1. Medial Prefrontal Cortex (mPFC)
Role:
- Self-referential thought
- Intention and goal processing
- Understanding self and others’ mental states
Effects of Damage:
- Blunted self-awareness
- Reduced introspection and autobiographical memory
- Difficulty in mentalizing—understanding others’ intentions
Symptoms & Behaviors:
- Flat affect or inappropriate self-perception
- Inability to reflect on one’s past or anticipate one’s future (identity fragmentation)
- Impaired social judgment: e.g., failing to recognize that a comment was offensive
- Example: In frontotemporal dementia, damage to the mPFC can cause loss of empathy, apathy, and inappropriate social behavior.
2. Temporoparietal Junction (TPJ)
Role:
- Distinguishing self from others
- Theory of Mind
- Perspective-taking
Effects of Damage:
- Confusion between self and other
- Deficits in attributing intentions to others
- Impaired moral reasoning
Symptoms & Behaviors:
- Autistic-like features: Difficulty understanding sarcasm, lying, or hidden motives
- Over-identification: Attributing one’s own thoughts to others, or vice versa
- Example: Right TPJ damage can impair the ability to pass false-belief tasks—classic tests of Theory of Mind.
3. Posterior Cingulate Cortex (PCC) & Precuneus
Role:
- Self-continuity
- Autobiographical memory
- Self in time (past/future)
Effects of Damage:
- Loss of narrative identity
- Disrupted sense of personal continuity
Symptoms & Behaviors:
- Amnesia for personal events, even if general memory is intact
- Disorientation about one’s life story or future goals
- Depersonalization: Feeling unreal or disconnected from one’s identity
- Example: In Alzheimer’s disease, early PCC disruption contributes to identity fragmentation.
4. Insula
Role:
- Interoception (body awareness)
- Embodied self-awareness
- Emotional salience
Effects of Damage:
- Disconnection from bodily self
- Blunted emotion or affect
- Loss of “gut-feeling” in social and moral decisions
Symptoms & Behaviors:
- Alexithymia: Difficulty identifying emotions
- Anosognosia: Denial of illness (common in right insula damage in stroke)
- Impaired empathy, especially emotional contagion
- Example: Damage can make a person fail to recognize that their heart is racing during fear—breakdown of the emotional self.
5. Superior Temporal Sulcus (STS)
Role:
- Perceiving others’ actions as intentional
- Reading gaze, posture, and biological motion
Effects of Damage:
- Others’ actions seem random or meaningless
- Breakdown in social nonverbal cues
Symptoms & Behaviors:
- Difficulty inferring goals from movement
- Impaired gaze following, important in joint attention
- Seen in autism spectrum disorders (hypoactivation of STS)
- Example: Patient may not interpret someone looking toward the door as intending to leave.
6. Anterior Cingulate Cortex (ACC)
Role:
- Emotional salience
- Conflict monitoring (self vs other)
- Empathy
Effects of Damage:
- Social apathy
- Poor emotional regulation
- Impaired conflict resolution (self vs group goals)
Symptoms & Behaviors:
- Lack of guilt or concern for others (can resemble psychopathy)
- Poor moral reasoning
- Flat social affect despite intact language or intelligence
Disorders Illustrating Disrupted Self/Other Representation:
Schizophrenia
- Hyperactivity or miswiring in the TPJ and DMN
- Symptoms: Delusions of control (“my thoughts aren’t mine”), auditory hallucinations (attributing one’s inner voice to others)
- Loss of self-boundaries—often thought to reflect faulty self-other distinction
Autism Spectrum Disorder (ASD)
- Hypoactivity in the mPFC, TPJ, and STS
- Symptoms: Difficulty understanding others’ perspectives, intentions, or sarcasm
- Often retain sense of self, but struggle with social cognition and teleology of others
Depersonalization Disorder
- Altered activity in insula and DMN
- Symptoms: Feeling detached from one’s body, as if observing oneself from outside
- Disruption of embodied self and continuity of identity
Ramblings 